In airports where bridges are used for passengers to pass from a terminal to a parked aircraft, various schemes have been devised for piping air, hot or cold, from an air heater or cooler on the ground, or in the terminal, to an aircraft. These heating and/or cooling units conventionally include piping for transmitting the hot or cold air from a source at the terminal end of the bridge to the aircraft and because a large volume of air needs to be piped, the piping is of large cross section; and because the bridges are extensible, the piping must be correspondingly extensible. Telescoping pipes have been used, but difficulties are encountered in sealing the joints between the telescoping sections and if the piping is bent or cocked, the joints tend to bind. Flexible hoses suspended in festoons from the telescoping bridge sections are subject to being run into by the many ground vehicles which swarm about a parked aircraft when it is being loaded or unloaded.